This project is aiming at developing a simple, easy to use system which projects a three dimensional image of the position of a colonoscope onto a video screen next to the endoscopic image. Specific goals for this phase I project are: 1) design and build a prototype sensor instrument which determines the position and posture of a colonoscope during operation, 2) develop the computer software needed to display the three dimensional image of the scope on a video screen, 3) evaluate instrument performance under conditions which simulate the in vivo environment. This system will play a major role in guiding colonoscopes through the colon to the cecum. It will increase the efficiency of colonoscopy, save time, and possibly decrease morbidity due to the procedure by reducing excess looping in the colon, a significant factor in colonic perforation. This study will lead to the specifications for a commercial endoscopic image detector instrument.